Photoresist composition and method pattern forming using the same

ABSTRACT

This invention relates to a negative photoresist composition with multi-reaction models. When the photoresist composition according to the present invention is used in photolithography processes employing UV light to produce cross-link reactions and multi-reactions including radical polymerization and cationic polymerization also occur. The photoresist composition can be used to control light reaction efficiency and increase reaction thoroughness, thus obtaining a high resolution pattern.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a photoresist composition and method ofpattern forming using the same. More particularly, the present inventionrelates to a photoresist composition with multi-reaction systems andmethod of pattern forming using the same.

[0003] 2. Description of the Related Art

[0004] With the progress of IC technologies, thin film photolithographyhas developed from G-line and I-line to deep UV and photoresistresolution processes have improved from 1 μm to less than 90 nm.

[0005] To conform to various electronics and optoelectronicsrequirements circuit board technology is evolving toward high densityinterconnection, fine pitch, and high aspect ratio. The thick filmphotolithography is the predominate process used in the above circuitboard technology, and offers improved exposure by employing uniformultraviolet (365 nm±10%) light as an exposure source.

[0006] The photoresist used in photolithography is usually dry film orliquid photoresist 10˜50 μm thick and with a 50 μm optimum resolution.Due to the multiple layer, and high distribution density requirements,the application of the present technology is limited. The circuit boardrequires a greater number of layers number to accommodate the longercircuit and the increased number of I/O points. Moreover, as electronicproducts become thinner and smaller, high density interconnection (HDI)substrates are the primary method of reducing manufacturing cost whilemaintaining the desired product size. Thus, photoresist resolution mustbe reduced to at least 10˜25 μm. Therefore, developing a simplephotoresist technology offering a complete figure, high aspect ratio,and superior resolution is necessary.

[0007] Currently the optimum HDI resolution is 50 μm as disclosed inU.S. Pat. No. 3,953,309, 5,087,552, and 5,609,991. The conventionalphotoresist technology employs a negative mono-reaction type (freeradical polymerization) photoresist using UV radiation to performphotolithography for a high density interconnection substrate.

[0008] When forming a high resolution photoresist pattern (with spacingwidth of less than 50 μm) using a conventional photoresist composition,the residual photoresist is difficult to remove and creates unevensurfaces due to defects such as distortion, swelling or raising,resulting from light scattering during exposure and the incompletereaction of photoresist composition, hence, the photolithographyresolution is limited.

[0009] The negative photoresist composition based on free-radicalpolymerization is highly reactive rate after exposure. The uniformity ofreaction suffers, however, due to the occurrence of complex anduncontrollable side-reactions resulting from the high reactivity offree-radicals. Thus, photoresist defects, such as distortion, swellingand raising, frequently remain after high resolution photolithography.

SUMMARY OF THE INVENTION

[0010] Accordingly, an object of the present invention is to provide anegative photoresist composition with multi-reaction systems. In the UVphotolithography process, the negative photoresist composition undergoesa cross-link reaction, and the multi-reaction systems performsimultaneously, wherein a multi-reaction system comprises free-radicalpolymerization and cation polymerization providing increased control anduniformity of reaction. As a result, the negative photoresistcomposition with multi-reaction systems can employed in advancedphotolithographic processes for various kinds of electronic devices andas it offers excellent cross-sectional profile, high fidelity and alkaliresistance. Moreover, high resolution (10-25 μm), high densityinterconnection substrates can be obtained by the photolithographyprocess employing negative photoresist composition according to thepresent invention.

[0011] Another object of the present invention is to provide a method offorming a photoresist pattern using the negative photoresist compositionaccording to the present invention to substantially prevent problemsresulting from the limitations and disadvantages of conventionalmethods.

[0012] To achieve the object of the present invention a negativephotoresist composition with multi-reaction systems comprising, auniform solution in an organic solvent, at least one saturated orunsaturated resin, at least one photoinitiator, at least one freeradical reactive monomer, at least one photoacid generator, and at leastone cation reactive monomer is provided.

[0013] The present invention additionally provides a method of patternforming using the previously described photoresist composition,including the following steps. A photoresist film is first formed on asubstrate using a negative photoresist composition according to thepresent invention. Next, a photoresist film with a predetermined patternis exposed to an actinic ray or radiation. Finally, the photoresist filmis developed with an alkaline developing solution to form a photoresistpattern.

[0014] In the present invention, the actinic ray can be uniformultraviolet light with a wavelength of about 365 nm.

[0015] A detailed description is given in the following embodiments withreference to the accompanying drawings

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention can be more fully understood by reading thesubsequent detailed description in conjunction with the examples andreferences made to the accompanying drawings, wherein:

[0017]FIGS. 1a and 1 b are scanning electron microscope (SEM)photographs illustrating comparative example 1.

[0018]FIGS. 2a and 2 b are scanning electron microscope (SEM)photographs illustrating comparative example 4.

[0019]FIGS. 3a and 3 b are scanning electron microscope (SEM)photographs illustrating comparative example 3.

DETAILED DESCRIPTION OF THE INVENTION

[0020] In order to further understand the present invention, thecomponents of the negative photoresist composition are described in thefollowing.

[0021] According to the present invention, the resin employed in thepresent invention has a molecular weight of between 5,000 and 250,000,and an acid value between 50 and 250 mgKOH/g. Preferably, the molecularweight of the resin is between 10,000 and 100,000, and has an acid valuebetween 70 and 150 mgKOH/g. The resin can also be a polymer withunsaturated bonds, and the examples include, but are not limited to,homopolymers and copolymers of at least one monomer selected fromstyrene, methyl styrene, acrylic acid, acrylate, methyl acrylic acid,methyl acrylate, vinyl ether, or derivatives thereof. Moreover, theresin can be acrylic resin, polyester, polyurethane, polyether, epoxyacrylate, or combinations thereof.

[0022] The photoinitiator suitable for use in the present invention isan agent which generates free radical species through decomposition byirradiation, such as benzoin, benzoin alkyl ether, benzil ketals,acetophenones derivatives, benzophenone,4,4′-dimethyl-aminobenzophenone, thioxanthones derivatives,morpholino-1-propanone, and combinations thereof. In addition, the atleast one photoinitiator is preferably present in an amount of 0.1-35parts by weight, most preferably 1-10 parts by weight, based on 100parts by weight of the at least one saturated or unsaturated resin.

[0023] The free radical reactive monomer is a monomer which can bepolymerized in the presence of free radicals, such as tetraethyleneglycol diacrylate, tetraethylene glycol dimethacrylate, neopentylglycoldiacrylate, neopentylglycol dimethyl acrylate, polyethylene glycoldiacrylate, polyethylene glycol dimethylacrylate, ethoxylated bisphenolA glycol diacrylate, ethoxylated bisphenol A glycol dimethyl acrylate,trimethylolpropane trimethacrylate, trimethylolpropane triacrylate,pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate,glyceryl propoxy triacrylate, pentaerythritol tetraacrylate,dipentaerythritol pentaacrylate, glycidyl acrylate, glycidylmethylacrylate, p-epoxy-styrene, pglycidyl-styrene, allyl glycidyl ether,3-glycidyloxy-propy 1-trimethoxy silane, β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, γ-glycidoxypropyl trimethoxysilane, and combinationsthereof. In addition, the at least one free radical reactive monomer ispreferably present in an amount of 0.1-100 parts by weight, mostpreferably 5-25 parts by weight, based on 100 parts by weight of the atleast one saturated or unsaturated resin.

[0024] The photoacid generator suitable for use in the present inventionis not particularly specific and can be any photoacid generator whichproduces acids by decomposition due to irradiation, such as onium salt,triarylsulfonium salt, alkylarylsulfonium salt, diaryliodonium salt,diarylchloronium salt, diarylbromonium salts, sulfonates, diazoniumsalt, diazonaphthoquinone sulfonate, and combinations thereof. Theexamples of triarylsulfonium salt include, but are not limited to,triaryl sulfonium hexafluorophosphate, triphenyl triflate, triphenylstibnite, methoxy triphenyl triflate, methoxy triphenyl stibnite, andtrimethyl triphenyl triflate. In addition, the at least one photoacidgenerator is preferably present in an amount of 0.1-35 parts by weight,most preferably 0.1-10 parts by weight, based on 100 parts by weight ofthe at least one saturated or unsaturated resin.

[0025] The cation reactive monomer can be a vinyl ether monomer or anepoxy monomer, such as cycloaliphatic diepoxide,N,N-diglycidyl-4-glycidyloxyaniline, 3,4-epoxycyclohexylmethylcarboxylate, 3,4-epoxycyclohexane carboxylate, 1,2-cyclohexanediglycidyl dicarboxylate, 1,4-cyclohexane dimethanol diglycidyl ether,ethylene glycol divinyl ether, diethylene glycol divenyl ether,triethylene glycol divinyl ether, 1,4-cyclohexane dimethanol divinylether, lactones or combinations thereof. In addition, the at least onecation reactive monomer is preferably present in an amount of 0.1-35parts by weight, most preferably 5-25 parts by weight, based on 100parts by weight of the at least one saturated or unsaturated resin.

[0026] While the essential ingredients in the photoresist compositionaccording to the present invention are the above described components,it is optional that the inventive photoresist composition is admixedwith at least one epoxy resin and/or at least one resin hardener. Theseadditional components are known and conventionally employed in negativephotoresist compositions.

[0027] The epoxy resin can be bisphenol A epoxy resin, brominated epoxyresin, phenolic novolac epoxy resin, cresol novolac epoxy resin,naphthalene epoxy, dicyclopendiene novolac epoxy, cycloaliphatic epoxy,isocyanate epoxy and combinations thereof. In addition, the at least oneepoxy resin is preferably present in an amount of 0.1-50 parts byweight, based on 100 parts by weight of the at least one saturated orunsaturated resin.

[0028] The resin hardener can be aliphatic amine, aromatic amine,polyamide, dicyandiamide, imidazoles, anhydride, and combinationsthereof.

[0029] The present invention is novel in that the negative photoresistcomposition according to the present invention undergoes a cross-linkreaction to simultaneously polymerize free-radicals and cations. Thephotoresist composition has high photosensitivity, and storage stabilitydue to the characteristics of multi-reaction systems. A feature of thepresent invention is that the negative photoresist composition includesvarious components which perform free-radical polymerizations and cationpolymerizations respectively by irradiation. Furthermore, the amounts ofeach component in the negative photoresist composition are designedwithin a particular range, resulting in improved control and uniformityof reaction.

[0030] The photoresist composition according to the present invention isnegative and alkali-soluble. When the negative photoresist compositionis exposed to actinic rays or radiation, the negative photoresistcomposition undergoes a cross-link reaction to simultaneously polymerizefree-radicals and cations resulting from acids and free-radical speciesintroduced by decomposition of photoinitiator and photoacid generatordue to irradiation. After exposure to irradiation, the exposed negativephotoresist composition is rendered alkali-insoluble, and can be removedby a weak alkaline solution.

[0031] The following comparative embodiments and embodiments areintended to illustrate the invention more fully without limiting theirscope, as numerous modifications and variations will be apparent tothose skilled in the art.

FIRST COMPARATIVE EXAMPLE

[0032] Resin A (acrylic resin, sold and manufactured under the tradenumber of 500 by Chang Chun Plastic Co., Ltd) having a molecular weightof 98500 and an acid value of 174 mg-KOH/g was dissolved in propyleneglycol monomethyl ether acetate (PMA) to prepare a resin solution havinga resin content of about 30%.

[0033] A mixture of 20.0 g of the obtained resin solution, 0.5 g of 2,4, or 6-trimethyl benzoyl diphenyl phosphine oxide (TPO) as aphotoinitiator, 0.8 of Irgacure 907 (available from Ciba Geigy), and0.20 g of isothioxanthone (ITX) was added into a round-bottom flask atroom temperature.

[0034] After mixing completely, 2.25 g of ditrimethylolpropanetetraacrylate (SR-355), 2.31 g of dipentaerythritol monohydroxypentaacrylate (SR-399), and 1.5 g of ethoxylated bisphenol A diacrylate(SR-349) were added to the resulting mixture. After mixing completely, aconventional negative photoresist composition was provided.

[0035] The ingredients and amounts of the above photoresist compositionare shown in Table 1. TABLE 1 Component Wt % Resin A 21.8 TPO 50.8 PMA1.8 Irgacure 907 2.9 ITX 0.7 SR-355 8.2 SR-399 8.4 SR-349 5.4

[0036] The photoresist composition as described above was coated on acopper clad laminate with a thickness of 10 μm, and the photoresistpatterns were designed respectively with a line/space resolution of 10μm and 15 μm to obtain a 1:1 line/space ratio. After exposure to uniformultraviolet light with a wavelength of about 365 nm and exposure energyof 150 mJ/cm2, the sample was developed by 1% sodium carbonate solutionwith ultrasonic agitation at 30° C. for 40 seconds to dissolve theunexposed area. The photoresist was developed to the ninth step in theStouffer 21 step guide.

[0037] The resist pattern after development was subjected to a scanningelectronic microscopy (SEM) photographic observation, as shown in FIGS.1a and 1 b. The obtained photoresist patterns had line widths of 13 μmand 20 μm respectively, and 10 μm and 15 μm with pre-determined designs.Individual line/space ratios were 2.2/1 and 2/1. In addition,photoresist defects, such as swelling and rising, were clearly observedin the SEM photographs of comparative example 1.

SECOND COMPARATIVE EXAMPLE

[0038] Resin B (styrene acrylic resin, sold and manufactured under thetrade number of Joncryl 690 by Johnson Polymer) having a molecularweight of 16500, a modified acid value of 200 mg-KOH/g and anunsaturated group of 7.13×10⁻⁴ mol/g was dissolved in propylene glycolmonomethyl ether acetate (PMA) to yield a resin solution with resincontent of about 40%.

[0039] A mixture of 20.0 g of the obtained resin solution, 2.0 g of 2,4, or 6-trimethyl benzoyl diphenyl phosphine oxide (TPO) as aphotoinitiator, 1.54 g of ditrimethylolpropane tetraacrylate (SR-355),0.75 g of dipentaerythritol monohydroxy pentaacrylate (SR-399), and 1.5of ethoxylated bisphenol diacrylate (SR-349) was added into around-bottom flask at room temperature. After mixing completely, aconventional negative photoresist composition was provided.

[0040] The ingredients and amounts of the above photoresist compositionare shown in Table 2. TABLE 2 Component Wt % Resin B 31.0 TPO 7.8 PMA46.5 SR-355 6.0 SR-399 2.9 SR-349 5.8

[0041] The photoresist composition as described above was coated on acopper clad laminate with a thickness of 10 μm. After exposure touniform ultraviolet light with a wavelength of about 365 nm and exposureenergy of 100 mJ/cm2, the sample was developed by 1% sodium carbonatesolution with ultrasonic agitation for 12 seconds to dissolve theunexposed area. The photoresist was developed to the ninth step in theStouffer 21 step guide.

[0042] The resist pattern after development was subjected to scanningelectronic microscopy (SEM) photographic observation. The line/spaceresolution of the obtained photoresist pattern was at least 25 μm widewhen the line/space ratio was 1:1.

THIRD COMPARATIVE EXAMPLE

[0043] Resin A (acrylic resin, sold and manufactured under the tradenumber of 500 by Chang Chun Plastic Co., Ltd) having a molecular weightof 98500 and an acid value of 174 mg-KOH/g was dissolved in propyleneglycol monomethyl ether acetate (PMA)to prepare a resin solution withresin content of about 30%.

[0044] A mixture of 20.0 g of the obtained resin solution, 4.5 g ofo-cresol novolac epoxy resin (sold and manufactured under the tradenumber of CNE200 by Chang Chun Plastic Co., Ltd) was added into around-bottom flask at room temperature.

[0045] After mixing completely, 1.5 g of cycloaliphatic diepoxide(SarCat®K126), 0.6 g of triaryl sulfonium hexafluorophosphate (50% inPropylene Carbonate) (SarCat®KI85), and 0.075 isothioxanthone (ITX) wereadded to the resulting mixture. After mixing completely, a conventionalnegative photoresist composition was provided.

[0046] The ingredients and amounts of the above photoresist compositionare shown in Table 3. TABLE 3 Component Wt % Resin A 20.85 PMA 55.95CNE2000 15.649 SarCat ®K126 5.21 SarCat ®K185 2.08 ITX 0.26

[0047] The photoresist composition as described above was coated on acopper clad laminate with a thickness of 10 μm. After exposure toscattering ultraviolet light with a wavelength of 200 to 400 nm andexposure energy of 500 mJ/cm2, the sample was subjected to apost-exposure bake (PEB) at 95° C. for 300 seconds. The sample wassubsequently developed by 1% sodium carbonate solution with ultrasonicagitation for 70 seconds to dissolve the unexposed area.

[0048] The resist pattern after development was subjected to a scanningelectronic microscopy (SEM) photographic observation. The line/spaceresolution of the obtained photoresist pattern is at least 30 μm whenthe line/space ratio was 1:1. The photoresist composition had thedisadvantages of scattering exposure source and higher desired exposureenergy.

FOURTH COMPARATIVE EXAMPLE

[0049] Resin A (acrylic resin, sold and manufactured under the tradenumber of 500 by Chang Chun Plastic Co., Ltd) having a molecular weightof 98500 and an acid value of 174 mg-KOH/g was dissolved in propyleneglycol monomethyl ether acetate (PMA) to prepare a resin solution havinga resin content of about 30%.

[0050] A mixture of 20.0 g of the obtained resin solution, 1.5 g ofcycloaliphatic diepoxide (SarCat®K126), 3.03 g of1,1,1-tris-(p-hydroxyphenyl) ethane glycidyl ether (THPE-GE) was addedto a round-bottom flask at room temperature.

[0051] After mixing completely, 1.212 g of triaryl sulfoniumhexafluorophosphate (50% in Propylene Carbonate) (SarCat®KI85), and0.152 isothioxanthone (ITX) were added to the resulting mixture. Aftermixing completely, a conventional negative photoresist composition wasprovided.

[0052] The ingredients and amounts of the above photoresist compositionare shown in Table 4. TABLE 4 Component Wt % Resin A 20.88 PMA 51.05THPE-GE 11.05 SarCat^(®)K126 11.05 SarCat ®K185 4.42 ITX 0.55

[0053] The photoresist composition as described above was coated on acopper clad laminate with a thickness of 10 μm, and the photoresistpatterns were designed respectively with a line/space resolution of 10μm and 15 μm to obtain a 1:1 line/space ratio. After exposure to uniformultraviolet light with a wavelength of about 365 nm and exposure energyof 700 mJ/cm², the sample was subjected to a post-exposure bake (PEB) at95° C. for 300 seconds. The sample was subsequently developed by 1%sodium carbonate solution with ultrasonic agitation 90 seconds todissolve the unexposed area.

[0054] The resist pattern after development was subjected to a scanningelectronic microscopy (SEM) photographic observation, as shown in FIGS.2a and 2 b. The obtained photoresist patterns had line widths of 9 μmand 13 μm respectively, with widths as low as 10 μm and 15 μm withpre-determined designs, and the individual line/space ratio was 0.8/1.In addition, photoresist defects, such as swelling and rising, wereclearly observed in the SEM photographs of comparative example 4.Moreover, the desired exposure energy of the above photoresistcomposition was higher.

FIRST EXAMPLE

[0055] Resin A (acrylic resin, sold and manufactured under the tradenumber of 500 by Chang Chun Plastic Co., Ltd) having a molecular weightof 98500 and an acid value of 174 mg-KOH/g was dissolved in propyleneglycol monomethyl ether acetate (PMA)to prepare a resin solution havinga resin content of about 30%.

[0056] A mixture of 20.0 g of the obtained resin solution, 0.5 g of 2,4, or 6-trimethyl benzoyl diphenyl phosphine oxide (TPO) as aphotoinitiator, 0.8 of Irgacure 907 (available from Ciba Geigy), and0.20 g of isothioxanthone (ITX) was added into a round-bottom flask atroom temperature.

[0057] After mixing completely, 2.31 g of ditrimethylolpropanetetraacrylate (SR-355), 2.25 g of dipentaerythritol monohydroxypentaacrylate (SR-399), 1.5g of ethoxylated bisphenol A diacrylate(SR-349), 0.125 g PS-104 (trade number, sold and manufactured by KOYOChemical Ins.) as a photoinitiator, and 2.0 g of ethylene glycol divinylether were added to the resulting mixture. After mixing completely, thenegative photoresist composition according to the present invention wasprovided.

[0058] The ingredients and amounts of the above photoresist compositionare shown in Table 5. TABLE 5 Component Wt % Resin A 20.2 TPO 47.2 PMA1.7 Irgacure 907 2.7 ITX 1.0 SR-355 7.6 SR-399 7.8 SR-349 5.1 PS-104 0.4Ethylene Glycol 6.7 Divinyl Ether

[0059] The photoresist composition as described above was coated on acopper clad laminate with a thickness of 10 μm, and the photoresistpattern was designed with a line/space resolution of 20 μm with a 1:1line/space ratio. After exposure to uniform ultraviolet light with awavelength of about 365 nm and exposure energy of 260 mJ/cm², the samplewas developed by 1% sodium carbonate solution with ultrasonic agitationfor 23 seconds with spray pressure of 1.0 kg/cm² to dissolve theunexposed area. The photoresist was developed to the ninth step in theStouffer 21 step guide.

[0060] The resist pattern after development was subjected to a scanningelectronic microscopy (SEM) photographic observation. The obtainedphotoresist patterns had line widths of 20 μm and line/space ratio of1/1, corresponding pre-determined designs.

SECOND EXAMPLE

[0061] Resin A (acrylic resin, sold and manufactured under the tradenumber of 500 by Chang Chun Plastic Co., Ltd) having a molecular weightof 98500 and an acid value of 174 mg-KOH/g was dissolved in propyleneglycol monomethyl ether acetate (PMA) to prepare a resin solution havinga resin content of about 30%.

[0062] A mixture of 20.0 g of the obtained resin solution, 0.25 g of 2,4, or 6-trimethyl benzoyl diphenyl phosphine oxide (TPO) as aphotoinitiator, 0.4 of Irgacure 907 (available from Ciba Geigy), and0.159 g of isothioxanthone (ITX) was added into a round-bottom flask atroom temperature.

[0063] After mixing completely, 1.967 g of ditrimethylolpropanetetraacrylate (SR-355), 2.02 g of dipentaerythritol monohydroxypentaacrylate (SR-399), 1.31 g of ethoxylated bisphenol A diacrylate(SR-349), 0.945 g of cycloaliphatic diepoxide (SarCat®K126) as a cationreactive monomer, and 0.473 g of triaryl sulfonium hexafluorophosphate(50% in Propylene Carbonate) (SarCat®K185) as a photoacid generator wereadded to the resulting mixture. After mixing completely, the negativephotoresist composition according to the present invention was provided.

[0064] The ingredients and amounts of the above photoresist compositionare shown in Table 6. TABLE 6 Component Wt % Resin A 21.8 TPO 50.9 PMA0.9 Irgacure 907 1.45 ITX 0.57 SR-355 7.15 SR-399 7.33 SR-349 4.76SarCat ®K126 3.4 SarCat ®K185 1.72

[0065] The photoresist composition as described above was coated on acopper clad laminate with a thickness of 10 μm, and the photoresistpattern is designed with a line/space resolution of 15 μm with a 1:1line/space ratio. After exposure to uniform ultraviolet light with awavelength of about 365 nm and exposure energy of 300 mJ/cm², the samplewas subjected to a post-exposure bake at 95° C. for 300 seconds. Thesample was subsequently developed by 1% sodium carbonate solution withultrasonic agitation for 70 seconds to dissolve the unexposed area.

[0066] The resist pattern after development was subjected to a scanningelectronic microscopy (SEM) photographic observation. The obtainedphotoresist patterns had line widths of 15 μm and the line/space ratiois 1/1, corresponding to that designed with pre-determined designs.

THIRD EXAMPLE

[0067] Resin A (acrylic resin, sold and manufactured under the tradenumber of 500 by Chang Chun Plastic Co., Ltd) having a molecular weightof 98500 and an acid value of 174 mg-KOH/g was dissolved in propyleneglycol monomethyl ether acetate (PMA)to prepare a resin solution havinga resin content of about 30%.

[0068] A mixture of 20.0 g of the obtained resin solution, 0.125 g of 2,4, or 6-trimethyl benzoyl diphenyl phosphine oxide (TPO) as aphotoinitiator, and 0.2 of Irgacure 907 (available from Ciba Geigy), wasadded into a round-bottom flask at room temperature.

[0069] After mixing completely, 1.125 g of ditrimethylolpropanetetraacrylate (SR-355), 1.155 g of dipentaerythritol monohydroxypentaacrylate (SR-399), 0.75 g of ethoxylated bisphenol A diacrylate(SR-349), 2.27 g of cycloaliphatic diepoxide (SarCatRK126) as a cationreactive monomer, 0.76 g of 1,1,1-tris-(p-hydroxyphenyl) ethane glycidylether (THPE-GE) and 0.61 g of triaryl sulfonium hexafluorophosphate (50%in Propylene Carbonate) (SarCatRK185) as a photoacid generator wereadded to the resulting mixture. After mixing completely, the negativephotoresist composition according to the present invention was provided.

[0070] The ingredients and amounts of the above photoresist compositionare shown in Table 7. TABLE 7 Component Wt % Resin A 22.23 TPO 51.88 PMA0.46 Irgacure 907 0.74 SR-355 4.16 SR-399 4.28 SR-349 2.78 SarCat ®K1268.43 THPE-GE 2.8 SarCat ®K185 2.24

[0071] The photoresist composition as described above was coated on acopper clad laminate with a thickness of 10 μm, and the photoresistpatterns were designed respectively with line/space resolutions of 10 μmand 15 μm with a 1:1 line/space ratio. After exposure to uniformultraviolet light with a wavelength of about 365 nm and exposure energyof 300 mJ/cm², the sample was subjected to a post-exposure bake at 95°C. for 300 seconds. The sample was subsequently developed by 1% sodiumcarbonate solution with ultrasonic agitation for 10 seconds to dissolvethe unexposed area. The photoresist was developed to the seventh step inthe Stouffer 21 step guide.

[0072] The resist pattern after development was subjected to a scanningelectronic microscopy (SEM) photographic observation, as shown in FIGS.3a and 3 b. The obtained photoresist patterns had line widths of 10 μmand 15 μm respectively and the line/space ratios are 1/1, correspondingto a pre-determined design.

[0073] The present invention has the following advantages.

[0074] After exposure to irradiation, the negative photoresistcomposition according to the present invention undergoes a cross-linkreaction to simultaneously polymerize free radicals and cations. Due tothe above multi-reaction systems, the polymerization uniformity of thephotoresist composition is increased, and the reactivity of thephotoresist composition is also controllable.

[0075] When the photoresist composition is coated on a printed circuitboard to form a photoresist film and exposed to UV light according to apredetermined pattern and developed with an alkaline developingsolution, a photoresist pattern having excellent cross-sectionalprofile, high fidelity and alkali resistance is formed. Moreover, highdensity interconnection substrates with high resolution (10-25 μm) canbe obtained by a photolithography process employing the negativephotoresist composition according to the present invention.

[0076] Furthermore, the negative photoresist composition according tothe present invention exhibits high photosensitivity. As a result, asource of exposure with lower and uniform energy, such as uniformultraviolet light, can be used to expose the photoresist composition inthe photolithography process in order to prevent the occurrence of thedistortion at the edge line of the photoresist pattern.

[0077] While the invention has been described by way of example and interms of the preferred embodiments, it is to be understood that theinvention is not limited to the disclosed embodiments. To the contrary,it is intended to cover various modifications and similar arrangements(as would be apparent to those skilled in the art). Therefore, the scopeof the appended claims should be accorded the broadest interpretation soas to encompass all such modifications and similar arrangements.

What is claimed is:
 1. A negative photoresist composition withmulti-reaction systems, comprising the following components as a uniformsolution in an organic solvent: at least one saturated or unsaturatedresin; at least one photoinitiator in an amount of 0.1 to 35 parts byweight, based on 100 parts by weight of the saturated or unsaturatedresin; at least one free radical reactive monomer in an amount of 0.1 to100 parts by weight; at least one photoacid generator in an amount of0.1 to 35 parts by weight; and at least one cation reactive monomer inan amount of 0.1 to 35 parts by weight.
 2. The negative photoresistcomposition as claimed in claim 1, wherein the multi-reaction systemscomprise free-radical polymerizations and cation polymerizations.
 3. Thenegative photoresist composition as claimed in claim 1, wherein thesaturated or unsaturated resin is selected from the group consisting ofhomopolymers, copolymers, and combinations thereof, which thehomopolymers and the copolymers are synthesized by at least one monomerselected from the group consisting of styrene, methyl styrene, acrylicacid, acrylate, methyl lacrylic acid, methyl acrylate, vinyl ether, andcombinations thereof.
 4. The negative photoresist composition as claimedin claim 1, wherein the saturated or unsaturated resin is selected fromthe group consisting of acrylic resin, polyester, polyurethane,polyether, epoxy acrylate and combinations thereof.
 5. The negativephotoresist composition as claimed in claim 1, wherein the saturated orunsaturated resin has a molecular weight in the range from 5,000 to250,000 and an acid value between 50 and 250 mgKOH/g.
 6. The negativephotoresist composition as claimed in claim 1, wherein the saturated orunsaturated resin has a molecular weight in the range from 10,000 to100,000 and an acid value between 70 and 150 mgKOH/g.
 7. The negativephotoresist composition as claimed in claim 1, wherein the at least onephotoinitiator is present in an amount of 0.1-10 parts by weight, basedon 100 parts by weight of the saturated or unsaturated resin.
 8. Thenegative photoresist composition as claimed in claim 1, wherein thephotoinitiator is selected from the group consisting of benzoin, benzoinalkyl ether, benzil ketals, acetophenones derivatives, benzophenone,4,4′-dimethyl-amino-benzophenone, thioxanthones derivatives,morpholino-1-propanone, and combinations thereof.
 9. The negativephotoresist composition as claimed in claim 1, wherein the at least onefree radical reactive monomer is present in an amount of 5-25 parts byweight, based on 100 parts by weight of the saturated or unsaturatedresin.
 10. The negative photoresist composition as claimed in claim 1,wherein the free radical reactive monomer is selected from the groupconsisting of tetraethylene glycol diacrylate, tetraethylene glycoldimethacrylate, neopentylglycol diacrylate, neopentylglycol dimethylacrylate, polyethylene glycol diacrylate, polyethylene glycoldimethylacrylate, ethoxylated bisphenol A glycol diacrylate, ethoxylatedbisphenol A glycol dimethyl acrylate, trimethylolpropanetrimethacrylate, trimethylolpropane triacrylate, pentaerythritoltriacrylate, ethoxylated trimethylolpropane triacrylate, glycerylpropoxy triacrylate, pentaerythritol tetraacrylate, dipentaerythritolpentaacrylate, glycidyl acrylate, glycidylmethyl acrylate,p-epoxy-styrene, p-glycidyl-styrene, allyl glycidyl ether,3-glycidyloxy-propy 1-trimethoxy silane, β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, γ-glycidoxypropyl trimethoxysilane, and combinationsthereof.
 11. The negative photoresist composition as claimed in claim 1,wherein the at least one photoacid generator is present in an amount of0.1-10 parts by weight, based on 100 parts by weight of the saturated orunsaturated resin.
 12. The negative photoresist composition as claimedin claim 1, wherein the photoacid generator is selected from the groupconsisting of onium salt, triarylsulfonium salt, alkylarylsulfoniumsalt, diaryliodonium salt, diarylchloronium salt, diarylbromonium salts,sulfonates, diazonium salt, diazonaphthoquinone sulfonate, andcombinations thereof.
 13. The negative photoresist composition asclaimed in claim 1, wherein triarylsulfonium salt is selected from thegroup consisting of triaryl sulfonium hexafluorophosphate, triphenyltriflate, triphenyl stibnite, methoxy triphenyl triflate, methoxytriphenyl stibnite, and trimethyl triphenyl triflate and combinationsthereof.
 14. The negative photoresist composition as claimed in claim 1,wherein the at least one cation reactive monomer is present in an amountof 5-25 parts by weight, based on 100 parts by weight of the saturatedor unsaturated resin.
 15. The negative photoresist composition asclaimed in claim 1, wherein the cation reactive monomer is selected fromthe group consisting of vinyl ether monomer, epoxy monomer, andderivatives thereof.
 16. The negative photoresist composition as claimedin claim 1, wherein the cation reactive monomer is selected from thegroup consisting of cycloaliphatic diepoxide,N,N-diglycidyl-4-glycidyloxyaniline, 3,4-epoxycyclohexylmethylcarboxylate, 3,4-epoxycyclohexane carboxylate, 1,2-cyclohexanediglycidyl dicarboxylate, 1,4-cyclohexane dimethanol diglycidyl ether,ethylene glycol divinyl ether, diethylene glycol divenyl ether,triethylene glycol divinyl ether, 1,4-cyclohexane dimethanol divinylether, lactones and combinations thereof.
 17. The negative photoresistcomposition as claimed in claim 1, further comprising: at least oneepoxy resin in an amount of 0.1 to 50 parts by weight, based on 100parts by weight of the saturated or unsaturated resin; and at least oneresin hardener in an amount of 0.1 to 30 parts by weight.
 18. Thenegative photoresist composition as claimed in claim 17, wherein theepoxy resin is selected from the group consisting of bisphenol A epoxyresin, brominated epoxy resin, phenolic novolac epoxy resin, cresolnovolac epoxy resin, naphthalene epoxy, dicyclopendiene novolac epoxy,cycloaliphatic epoxy, isocyanate epoxy and combinations thereof.
 19. Thenegative photoresist composition as claimed in claim 17, wherein theresin hardener is selected from the group consisting of aliphatic amine,aromatic amine, polyamide, dicyandiamide, imidazoles, anhydride andcombinations thereof.
 20. A method of forming pattern using a negativephotoresist composition with multi-reaction systems, comprising: forminga photoresist film on a substrate using a negative photoresistcomposition, wherein the negative photoresist composition comprises thefollowing components as a uniform solution in an organic solvent: atleast one saturated or unsaturated resin; at least one photoinitiator inan amount of 0.1 to 35 parts by weight, based on 100 parts by weight ofthe saturated or unsaturated resin; at least one free radical reactivemonomer in an amount of 0.1 to 100 parts by weight; at least onephotoacid generator in an amount of 0.1 to 35 parts by weight; at leastone cation reactive monomer in an amount of 0.1 to 35 parts by weight;providing an actinic ray or radiation to expose predetermined patternsof the photoresist film; and developing the photoresist film with analkaline developing solution.
 21. The method as claimed in claim 20,wherein the actinic ray is a uniform ultraviolet with a wavelength about365 nm.